S-(−)-9-Fluoro-6,7-dihydro-8-(4-hydroxypiperidin-1-yl)-5-methyl-1-oxo-1H,5H-benzo[i,j]quinolizine-2-carboxylic acid L-arginine salt is a broad-spectrum antibiotic, medically grouped together with the fluoroquinolone class of antibiotics, which is disclosed and claimed in our U.S. Pat. No. 6,514,986 B2 as being isolated in a less crystalline anhydrate form and a more crystalline hydrate form. Our U.S. Pat. No. 6,664,267 describes a crystalline monohydrate form of S-(−)-9-fluoro-6,7-dihydro-8-(4-hydroxypiperidin-1-yl)-5-methyl-1-oxo-1H,5H-benzo[i,j]quinolizine-2-carboxylic acid L-arginine salt that is disclosed as having advantages over the anhydrate and hydrate forms described in U.S. Pat. No. 6,514,986 B2. Such advantageous properties for the crystalline monohydrate form, in comparison to the less crystalline anhydrate and hydrate forms, include enhanced stability at specified conditions of humidity and temperature.
In accordance with the present invention, it has been found that S-(−)-9-fluoro-6,7-dihydro-8-(4-hydroxypiperidin-1-yl)-5-methyl-1-oxo-1H,5H-benzo[i,j]quinolizine-2-carboxylic acid L-arginine salt tetrahydrate in highly homogeneous form is advantageous over previously known forms and may be usable to prepare stable pharmaceutical dosage forms, including an aqueous solution, because it is the most physically stable form and does not have a tendency over time to convert to other crystalline forms.